Process for recycling denim waste

ABSTRACT

Denim fabric suitable for use as apparel is made from 40-100% fibers produced from denim waste (pre-consumer and/or post-consumer). The denim waste is collected, starch and size are removed, and it is subjected to garnetting to produce denim fibers, the vast majority of fiber lengths greater than about 0.4 inches, and an average length greater than 0.5 inches. The denim fibers are then opened, and subjected to low-tension carding, as by using a Rieter C-4 card with conveyor belt. The carded denim fibers are spun into filling yarn having a yarn count between about 4.0/1 to 16.0/1, and/or a warp or knitting yarn having a yarn count between about 4.0/1 to 16.0/1. The warp or knitting yarn may be plied with like reclaimed warp yarn, or with virgin fiber warp yarn. There may also be the steps of adding lubricant to the fibers, sorting the denim waste by color and separately processing different colors of denim waste, making the denim fabric into apparel, dyeing the yarn or fabric to provide a substantially uniform color or fabric, and/or cleaning the fibers between the opening and carding steps. The denim fabric produced has strength and related properties sufficient for consumer use.

BACKGROUND AND SUMMARY OF THE INVENTION

In an era of scarce resources and increasing population, it is desirableto reclaim and reuse as many resources as possible. In the textileindustry, for many years wool clothing and other types of woolenproducts have been torn apart using a process known as garnetting andthe fibers reused in clothing and wool rugs. Garnetting is a process bywhich material such as threads, rags, woven cloth scraps, and the likeare broken up and returned to a substantial fluffy, fibrous conditionsimulating the original condition of the fiber. This is done by firstchopping the material to small pieces (e.g. two to six inches) and thenrunning the pieces through a series of high speed cylinders which can becovered with wire (e.g. saw wire), steel spikes, or the like. Thetreatment breaks up the material into individual fibers typically havinga length of one and one-eighth inches or less.

Despite the known desirability of reusing resources, and the knownrecycling of woolen products for many years, attempts to reclaim andreuse cotton fibers from old garments, scraps and rags have encounteredlarge obstacles which have always prevented the development of apractical, commercial approach. Garnetting or separation of the cottonfiber from the original materials must be severe enough to cause fiberseparation, but in so processing the materials, the fibers produced weredamaged and broken. The result was very short fibers, typically ofone-half inch or less, which are too short to make into yarn and fabricusing commercial processes. Therefore the recycling or reclamation ofcotton fibers has typically been restricted to the production of low endtextile products, such as mops or non-woven materials.

According to the present invention, a method and fabric are providedwhereby denim cotton fibers can effectively be reclaimed. The fabricproduced according to the invention has properties comparable to that ofdenim fabric made from virgin yarn, and is suitable for essentially allapparel applications that virgin denim yarn may be used for. While theinvention is also useful in association with post-consumer denim wastematerial, it is particularly useful to employ pre-consumer denim wastesuch as cutting table scraps of denim cotton fabrics, actual cottonthread, denim yarn waste, and denim fabric scraps left over from tilecutting out of patterns for garments. This has an enormous potential forresource recovery due to the large volume of denim garments that areproduced yearly, from indigo dyed denim and sulfur black dyed denim andother colors using millions of pounds of cotton each year. For example,the consumption of cotton for denim fabric in the United States during1992 was over 800 million pounds. Cloth scraps make up approximately 10%of this amount, depending upon patterns cut, meaning that there ispresently annual waste to landfills or incinerators for denim scrapsalone of close to 80 million pounds per year since the markets for thelow end textile products using cotton fibers typically do not employdenim, or if they do only a small fraction of tile denim waste thatexists is employed.

According to the invention, denim yarns and denim fabrics can beproduced containing from 40% to 100% (preferably 60-100%) of reclaimedcotton from pre-consumer denim waste and/or post-consumer denim waste.According to the present invention it has been found that if theappropriate treatment steps are practiced and if the garnetted scrapmaterial is carded in a low tension manner, it is possible to spin yarnfrom the reclaimed denim waste fibers, and produce yarns for weaving orknitting, e.g. filling yarn having a yarn count of 4.0/1 to 12.0/1, andwarp yarn (for plying with itself or with virgin yarn) having a yarncount of about 9.0/1 to 16.0/1.

According to one aspect of the present invention a method of makingdenim fabric is provided comprising tile steps of substantiallysequentially: (a) Collecting denim waste. (b) Removing starch and sizefrom the denim waste. (c) Garnetting the denim waste to produce denimfibers with the vast majority having fiber lengths greater than about0.4 inches (and the average fiber length greater than 0.5 inches). (d)Opening the denim fibers. (e) Low-tension carding the opened denimfibers. (f) Spinning the carded denim fibers into yarn. And, (g) weavingor knitting the yarn into fabric having at least about 40% of the totalfiber content of the fabric from the denim waste collected in step (a).

There may also be the further steps of adding lubricant to the fibersbetween steps (c) and (d), sorting the denim waste by color betweensteps (a) and (b) and separately processing different colors of denimwaste, making the denim fabric into denim apparel, and after either step(f) or step (g) dyeing the yarn or fabric to produce a substantiallyuniform color of fabric. There may also be the further step, between theopening and carding steps, of cleaning the fibers, as with an ERMfeeder. There also may be the further step of adding some virgin denimfiber, up to about 50% (preferably up to about 40%) of the total fibercontent, to the denim fibers from step (c) prior to step (e).

Where step (g) is weaving, step (f) is practiced to produce fillingyarns; step (f) is also typically practiced to produce yarn and step (g)is practiced using both filling and warp or knitting yarn from step (f).There is also the option of a further step of plying tile warp yarnsfrom step (f) together before practicing step (g), or plying warp yarnsfrom step (f) together with virgin denim yarn before practicing step(g).

Step (b) is typically practiced by treating the denim material withamylase enzyme. Step (a) may be practiced by collecting pre-consumerdenim waste only, or by collecting post-consumer denim waste, or bothpre-consumer and post-consumer denim waste. For the post consumer denimwaste there is tile further step of removing non-denim materials fromthe waste prior to other processing. Also steps (f) and (g) may bepracticed to produce denim fabric having approximately 100% of the fibercontent thereof from the fiber collected in step (a), and step (e) maybe practiced using a Rieter C-4 card with a conveyor belt.

According to another aspect of the present invention a woven denimfabric having warp and filling yarns is provided by practicing the stepsof the method set forth above. Step (f) may also be practiced to makethe warp yarn, where the filling yarn of the fabric has a yarn count ofabout 4.0/1 to 12.0/1, and the warp yarn is warp yarn from step (f)having a yarn count of about 4.0/1 to 16.0/1 and could be plied withother warp yarn from step (f), or with virgin denim yarn.

One aspect of the present invention is a knitted fabric made from yarnsproduced in step (f).

According to another aspect of the present invention a woven denimfabric is provided having filling and warp yarns. The fabric hassubstantially 100% of the filling yarn made from pre-consumer,post-consumer, or both pre-consumer and post-consumer denim waste, andhas at least about 40% of the total of filling and warp yarns made frompre-consumer, post-consumer, or both pre-consumer and post-consumerdenim waste. The fabric may have about 100% of the total of filling andwarp yarns made from pre-consumer, post-consumer, or both pre-consumerand post-consumer denim waste.

The invention also contemplates a knit denim fabric made by practicingthe steps of substantially sequentially: (a) collecting denim waste; (b)removing starch and size from the denim waste; (c) garnetting the denimwaste to produce denim fibers having the vast majority of the fiberlengths greater than about 0.4 inches; (d) opening the denim fibers; (e)low-tension carding the opened denim fibers; (f) spinning the cardeddenim fibers into yarn; and (g) knitting the yarn into fabric having atleast about 40% of the total fiber content of the fabric from the denimwaste collected in step (a).

It is the primary object of the present invention to makeapparel-quality denim fabric (and apparel therefrom) from denim waste.This and other objects of the invention will become clear from aninspection of the derailed description of the invention and from theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic box diagram schematically illustrating exemplarymethod steps in the practice of the method according to the presentinvention:

FIG. 2 is a side schematic view illustrating an exemplary cleaner usedin practicing the "clean" step of FIG. 1; and

FIG. 3 is a schematic view illustrating the operation of a low-tensioncard machine in the practice of the method of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an exemplary method of producing denimcloth, apparel, or knitted garments from denim waste. The first step inthe process is the collection of pre-consumer denim waste as indicatedby box 10 in FIG. 1. The term "pre-consumer denim waste" means cuttingtable scraps of denim cotton fabrics, natural cotton thread, denim yarnwaste, and denim fabric scraps left over from the cutting out ofpatterns for garments. While the collection and use of only pre-consumerdenim waste (as indicated by box 10) is the simplest manner ofpracticing the present invention, optionally according to the presentinvention, post-consumer denim waste may also be collected forutilization, as indicated by box 11 in FIG. 1, along with, or insteadof, the pre-consumer denim waste collected as indicated at box 10. Ifpost-consumer denim waste, such as from old clothes repositories, ragcompanies, or the like, is collected as indicated by box 11, it isnecessary to remove all the non-denim materials therefrom as indicatedby box 12. Particularly zippers, buttons, rivets, leather patches,non-wovens, or other foreign materials would have to be removed beforethe denim waste could be utilized, and such removal may have to beaccomplished by hand to ensure a raw material of sufficient integrity.

After collection of the denim waste as indicated by box 10 (and/or boxes11,12) preferably the denim waste is sorted by color, eitherautomatically using an optical sorter, or by hand. The two most commoncolors are indigo dyed (blue) and sulfur dyed black denim, althoughother colors are of course known. After separation by color in box 14,the different color streams are processed separately, and the rest ofthe schematic of FIG. 1 illustrates the processing for one of the colorsorted streams (e.g. an indigo dyed (blue) stream).

The first step after color sorting is a treatment to remove starch andsize, as indicated by box 15 in FIG. 1. Preferably this is accomplishedutilizing amylase enzyme which converts starch on the yarn or fabric tosugar, which is water soluble and can be washed out of the fabric or theyarn. Such a treatment is typically about 15 minutes long, and may beeffectively practiced by adding 1-2% on weight of scraps of RAPIDASE-XL,a trademark for amylase enzyme manufactured by International BioSynthetics, at 140° F. This 15 minute enzyme treatment at 140° F. isfollowed by a rinse bath for five minutes at 140° F. which extracts thesugar, and then by tumble drying. The equipment utilized to practicethis treatment is typically commercial type washing and drying machines.A batch process is presently the most desirable since it utilizesconventional machines, but a continuous process can also be designed.Alternatively, the treatment of box 15 could be practiced by acidhydrolysis.

Alter box 15 the denim waste is subjected to garnetting as indicated bybox 16. As described above, garnetting is a process by which materialssuch as threads, rags, woven cloth scraps, and the like are broken upand returned to a fluffy, fibrous condition, simulating the originalcondition of the cotton fiber. This is preferably accomplished by firstchopping the denim waste into smaller pieces (e.g. 2-6 inch maximumdimension), and then running it through a series of high speedcylinders. The cylinders are typically covered by wire (e.g. saw wire),steel spikes, or the like. Garnetting breaks down the denim waste intoindividual cotton fibers. While any fiber length greater than about 0.4inches is useful, garnetting rarely produces fibers having a length ofgreater than one and one-eighth inches. Lengths of about 0.4-0.8 inchesare typical, with a length of about 0.6 inches (i.e. over 0.5 inches)being about average, and the vast majority (e.g. more than 90%) over 0.4inches in length.

After garnetting, lubricant may be added as indicated by box 17. Thelubricant is added to reduce friction among fibers when processing,particularly in subsequent carding and spinning processes. Typicallubricants are high density emulsified polyethylene (e.g. Moropol HD-25available from Moretex Chemical Company), fatty amide (e.g. SEDGESOFTSTT-2 available from Sedgefield Chemical Company), and sulfatedquaternary amine (e.g. SEDGESOFT LVC-2 available from SedgefieldChemical Company).

After lubricant is added, the denim waste is processed--as indicated bybox 18--through a fiber control hopper/feeder of conventional design toan opener, as indicated by box 19. A typical opener that is suitable isa Rieter fine opener (Model ERMB-55 for example). Typically afteropening at box 19 the material is cleaned as indicated generally by box20 in FIG. 1, and by the apparatus 20 of FIG. 2.

As illustrated schematically in FIG. 2, the ERM-cleaner 20 includes amaterial supply 21 extending from the opening stage 19, terminating in afeed head with fan 22 at the top of a laminar chute 25 filled with thematerial. Exhaust air piping 23 is also provided, as well as a conduit24 for delivery of the cleaned material to the carding step (36 in FIG.1).

The cleaner 20 further comprises a plain drum 26, dust cage 27, and feedrollers 28. Below the feed rollers 28 is a knife grid 29 and an openingand cleaning beater 30, a suction duct 31 pulling the cleaned fiber intothe delivery conduit 24. A motor 33 drives the opening and cleaningbeater 30. Surrounding the knife grid 29 is the waste chamber 32, whichcan be connected to an automatic waste removal system, which wouldinclude the waste removal pipe 34.

After the conventional cleaning stage 20, the fibers are transmitted tothe low tension card stage 36 illustrated by a box diagram in FIG. 1 andschematically in FIG. 3. It is necessary to handle the fibers so thatthere is minimum tension or strain on the web 38 being discharged fromthe head 37 on the card 36. This is accomplished by simply depositingthe web 38 in basically loose form 39 on a conveyor belt 40 whichconveys the material 39 slowly to the trumpet 41. Downstream of thetrumpet 41 are rollers 42 which convey the silver rope 43 that is formedafter passage of the material 39 through the trumpet 41 to a take-updevice (coiler) 44 for the silver rope 43. The card 36 illustratedschematically in FIG. 3 is preferably a Rieter C-4 Card (e.g. C4-A),which is commercially available from Rieter Machine Works Ltd. ofSwitzerland.

From the coiler 44, the sliver rope 43 is ultimately (typically at adifferent machine location) passed to a spinning stage illustratedschematically at 46 in FIG. 1. For example the spinning stage 46 mayutilize a Rieter open-end conventional spinning frame. Differentspinning machines, illustrated schematically by box 46, may be utilizedto produce both filling and warp yarn. The open end yarn produced by thespinning stage 46 may produce filling yarn--indicated schematically at47 in FIG. 1--into counts of 4.0/1 to 16.0/1 (e.g. 4/1 to 12/1, withabout 5.25/1 being typical), while warp or knitting yarn--illustratedschematically at 48 in FIG. 1--can be made having counts of 4.0/1 to16.0/1 (e.g. 9.0/1 to 16.0/1). Preferably the warp yarn 48, before beingwoven into cloth in a loom, as indicated schematically at 49 in FIG. 1,is plied (using conventional plying techniques) either with other warpyarns 48, or with virgin denim warp yarn 51 from source 50. Singles yarnmay also be used.

The cloth produced by the weaving stage (loom) 49 has at least about 40%of the total fiber content thereof from the denim waste collected instages 10 and/or 11, and may contain up to about 100% fiber from stages10/11. Woven cloth made from reclaimed denim filling and warp yarns hasbeen produced and tested, with the results indicating that the fabrichas the strength and other characteristics sufficient for the resultantfabric to be used in the manufacture of apparel. As indicated by box 53in FIG. 1, the woven cloth produced by loom 49 may be made into denimapparel, the cloth produced by loom 49 being suitable for virtually anyapplication which currently uses denim fabric.

As earlier indicated, instead of weaving the yarn into fabric, the yarnfrom 46 may be knit into a denim fabric, such as generally taught inU.S. Pat. No. 4,613,336 (the disclosure of which is hereby incorporatedby reference herein).

Under some circumstances it may be desirable to dye the yarn, cloth, orgarments produced so that they have a substantially uniform color. Thisis indicated schematically at 55 in FIG. 1, the options of dyeing thefilling and/or warp (or knitting) yarns 47, 48, the cloth produced byloom 49, or the garments produced from stage 53, all being possible.

Instead of, or in addition to, supplying as part of the warp or knittingyarn virgin denim yarn from source 50, from 0-50% (preferably 0-40%) ofthe fiber led to the opener 19 (i.e. before carding at 36) may be virginyarn--e.g. from source 57 seen in FIG. 1--so that the spun yarn producedat 46 itself has between 0-50% virgin fiber. In this case it is fromless desirable to totally unnecessary to ply the yarn produced at 46with virgin denim yarn from 50.

It will thus be seen that according to the present invention a woven orknit denim fabric may be produced, a woven fabric having filling andwarp yarns, with substantially 100% of the filling yarn made frompre-consumer, post-consumer, or both, denim waste, and having at leastabout 40% (preferably at least about 60%) of the total filling and warpyarns made from pre-consumer, post-consumer, or both, denim waste, andadvantageous methods of producing such fabric, and garments therefrom,are provided, and a knit fabric produced with up to 100% reclaimed fiberin counts of 4/1-16/1. While the invention has been herein shown anddescribed in what is presently conceived to be the most practical andpreferred embodiment thereof, it will be apparent to those of ordinaryskill in the art that many modifications may be made thereof within thescope of the invention, which scope is to be accorded the broadestinterpretation of the appended claims so as to encompass all equivalentproducts and methods.

What is claimed is:
 1. A method of making denim fabric comprising tilesteps of substantially sequentially:(a) collecting denim waste; (b)removing starch and size from tile denim waste; (c) garnetting tiledenim waste to produce denim fibers having the vast majority of fiberlengths greater than about 0.4 inches; (d) opening the denim fibers; (e)low-tension carding the opened denim fibers; (f) spinning tile cardeddenim fibers into yarn; and (g) weaving or knitting tile yarn intofabric having at least about 40% of the total fiber content of thefabric from the denim waste collected in step (a).
 2. A method asrecited in claim 1 comprising tile further step, between steps (c) and(d), of adding lubricant to the fibers to reduce friction among fibersduring tile practice of steps (e) and (f).
 3. A method as recited inclaim 1 wherein step (g) is practiced by weaving, and step (f) ispracticed to produce filling yarn.
 4. A method as recited in claim 3wherein step (f) is also practiced to produce warp yarn, and whereinstep (g) is practiced using both filling and warp yarn from step (f),and wherein step (c) is practiced so that the average length of fiberproduced is greater than 0.5 inches.
 5. A method as recited in claim 4comprising the further step of plying warp yarns from step (f) togetherbefore practicing step (g).
 6. A method as recited in claim 4 comprisingthe further step of plying warp yarns from step (f) together with virgindenim yarn before practicing step (g).
 7. A method as recited in claim 1comprising the further step of adding some virgin denim fiber, up toabout 50% of the total fiber content, to the denim fibers from step (c)prior to step (e).
 8. A method as recited in claim 1 wherein step (g) ispracticed by knitting the yarn into fabric.
 9. A method as recited inclaim 8 wherein steps (f) and (g) are practiced to produce knitting yarnhaving a yarn count between about 4.0/1 to 16.0/1.
 10. A method asrecited in claim 1 wherein step (b) is practiced by treating the denimmaterial with amylase enzyme.
 11. A method as recited in claim 1 whereinstep (a) is practiced by collecting only pre-consumer denim waste.
 12. Amethod as recited in claim 1 wherein step (a) is practiced by collectingpost-consumer denim waste, and comprising the further step of removingnon-denim materials from the post-consumer denim waste.
 13. A method asrecited in claim 1 wherein step (a) is practiced by collecting bothpre-consumer and post-consumer denim waste, and comprising the furtherstep of removing non-denim material from the post-consumer denim waste.14. A method as recited in claim 1 comprising tile further step, betweensteps (a) and (b), of sorting the denim waste by color, and separatelyprocessing different colors of denim waste.
 15. A method as recited inclaim 1 comprising tile further step of making the denim fabric intodenim apparel.
 16. A method as recited in claim 3 wherein steps (f) and(g) are practiced to produce denim fabric having approximately 100% ofthe fiber content thereof from the fiber collected in step (a).
 17. Amethod as recited in claim 1 comprising the further step, after eitherstep (f) or step (g), of dyeing the yarn or fabric to provide asubstantially uniform color of fabric from step (g).
 18. A method asrecited in claim 1 wherein step (e) is practiced using a Rieter C-4 cardwith conveyor belt.
 19. A method as recited in claim 1 comprising thefurther step of cleaning the fibers between steps (d) and (e), andwherein step (g) is practiced to produce fabric having at least about60% of the total fiber content of the fabric from the denim wastecollected in step (a).
 20. A method as recited in claim 4 wherein steps(f) and (g) are practiced to produce filling yarn having a yarn countbetween about 4.0/1 to 16.0/1, and warp yarn having a yarn count betweenabout 4.0/1 to 16.0/1.